how to resample 8 kHz to 48 kHz,what is the suggestion?

[ChampionL]

now ,i have a 8k pcm, if i apply this project to my pcm,i need resample 8khz to 48khz,what method of sampling i clould apply and make no effect on noise reduction?

[cogmeta]

You can either duplicate and interpolate the values.

[csetanmayjain]

You can use audacity software for it or using sox command

[richardpl]

No, best use ffmpeg.

[csetanmayjain]

Yeah, ffmpeg can be used

[piotrgregor]

You can upsample it with https://github.com/dataandsignal/libhdsp this way:

hdsp_status_t hdsp_upsample_int16(int16_t *x, size_t x_len, int upsample_factor, int16_t *y, size_t y_len);

A more complete snippet may look like this:

#include "hdsp.h"

int main(int argc, char **argv) {

    #define Fs_x 8000
    #define f_x 200
    #define Fs_y 48000
    #define FRAME_LEN_MS 20
    #define X_LEN_SAMPLES (FRAME_LEN_MS * Fs_x / 1000)
    #define Y_LEN_SAMPLES (FRAME_LEN_MS * Fs_y / 1000)
    #define UPSAMPLE_FACTOR (Fs_y / Fs_x)

    int16_t x[X_LEN_SAMPLES] = {0};
    int16_t y[Y_LEN_SAMPLES] = {0};

    int i = 0;
    while (i < X_LEN_SAMPLES) {
        x[i] = 100 * sin((double)i * 2 * M_PI * f_x / Fs_x);
        printf("%d\n",x[i]);
        i = i + 1;
    }

    hdsp_test(HDSP_STATUS_OK == hdsp_upsample_int16(x, X_LEN_SAMPLES, UPSAMPLE_FACTOR, y, Y_LEN_SAMPLES), "It did not work\n");

    i = 0;
    while (i < X_LEN_SAMPLES)
    {
        int j = 0;
        while (j < UPSAMPLE_FACTOR) {
            if (j == 0) {
                hdsp_test(y[UPSAMPLE_FACTOR * i + j] == x[i], "Wrong sample");
            } else {
                hdsp_test(y[UPSAMPLE_FACTOR * i + j] == 0, "Wrong zero");
            }
            j = j + 1;
        }
        i = i + 1;
    }
    return 0;
}

Here is an article I wrote about upsampling / downsampling and filtering using libhdsp (I am author of this lib):

https://dataandsignal.com/blog/static/audio_upsampling_downsampling_and_filtering_with_libhdsp/

And here I wrote a tool that integrates RNNoise, so you can just:

./hdsptool denoise <input file raw> <input file sample rate> <frame ptime ms>

https://github.com/dataandsignal/libhdsp/blob/master/test/hdsptool.c